Cytogenetic findings in lymphoplasmacytic lymphoma/Waldenström macroglobulinemia. Chromosomal abnormalities are associated with the polymorphous subtype and an aggressive clinical course

CD137 (ILA/4-1BB), a member of the tumor necrosis factor receptor family, and its ligand are expressed on activated T lymphocytes and on antigen-presenting cells, respectively. Via bidirectional signal transduction, this receptor-ligand system regulates the activation, proliferation, and survival of T and B lymphocytes and monocytes. We used immunohistochemical studies on human tissue samples to determine in vivo CD137 expression in nonimmune tissue samples. Strong CD137 expression was found in blood vessel walls, on the endothelial layer, and on the vascular smooth muscle cells. But in 32 healthy tissue samples examined, none contained CD137-positive vessels. Also, in benign tumors (2/14) and in inflammatory tissues (2/9) only a minority had CD137-expressing vessels. However, malignant tumors had a significantly enhanced frequency of CD137-expressing blood vessels (11/34).     

Characterisation of soluble murine CD137 and its association with systemic lupus

CD137 is a member of the tumor necrosis factor receptor family, and is involved in the regulation of activation, proliferation, differentiation and apoptosis of T cells, B cells, monocytes, dendritic cells, natural killer cells and granulocytes. Here report that soluble forms of murine CD137 (sCD137) are generated by differential splicing and are released by activated T cells. Levels of sCD137 correlate with cell activation and the extent of cell death but not with cellular proliferation. While CD8(+) T cells express significantly more cell surface CD137 than CD4(+) T cells, both T cell subsets express similar levels of sCD137, resulting a twofold increased ratio of soluble to cell surface CD137 for CD4(+) T cells. sCD137 exists as a trimer and a higher order multimer, can bind to CD137 ligand, and inhibits secretion of IL-10 and IL-12. sCD137 is present in sera of mice with autoimmune disease but is undetectable in sera of healthy mice.     

CD137 is expressed by follicular dendritic cells and costimulates B lymphocyte activation in germinal centers

CD137, a member of the TNF receptor family, and its ligand are expressed on T lymphocytes and antigen-presenting cells (APC), respectively. During interaction with APC, T lymphocytes receive a potent, costimulatory signal through CD137. Reverse signaling has been demonstrated for the CD137 ligand, which causes activation in monocytes. Here we show that B lymphocytes also receive costimulatory signals through the CD137 ligand. Immobilized CD137 augmented proliferation of preactivated B lymphocytes up to fivefold and immunoglobulin synthesis, up to threefold. CD137 had no effect on resting cells. Further, we show that CD137 is expressed in vivo by follicular dendritic cells (FDC) in germinal centers. Germinal centers form during humoral immune responses and are essential for B lymphocyte affinity maturation. These data imply that, similar to the CD40 receptor/ligand system, which mediates T lymphocyte help to B lymphocytes after the first antigen encounter, the CD137 receptor/ligand system may mediate costimulation of B lymphocytes by FDC during affinity maturation.     

Differential effects of interleukin-10 on the expression of HLA class II and CD1 molecules induced by granulocyte/macrophage colony-stimulating factor/interleukin-4

Interleukin (IL)-10 down-regulates HLA class II molecules, whether constitutively expressed or up-regulated by interferon-γ or IL-4 on monocytes but not on B lymphocytes. In this study we show that IL-10 does not inhibit HLA class II expression induced by the combination granulocyte/macrophage colony-stimulating factor and IL-4 on monocytes, although it simultaneously abrogates the expression of CD1 molecules induced by the same combination of cytokines. CD1 molecules can act as element of genetic restriction for CD4^? CD8^? T lymphocytes, and the suppression of CD1 expression by IL-10 abolished antigen presentation to CD1-restricted CD4^? CD8^? T cell receptor-positive T cells. Although HLA class II expression was not down-regulated by IL-10, the antigen specific proliferative response of CD4⁺ T cells was nevertheless decreased. This was not caused by down-regulation of known co-stimulatory molecules such as B7.1, B7.2 and ICAM-1. IL-10 decreased the antigen specific proliferative response further by directly influencing the T lymphocytes. Our results indicate that IL-10 exerts some of its immunoregulatory functions by differential modulation of antigen presenting molecules, induced by the same combination of cytokines.     

Kinetics of cytokine release and expression of lymphocyte cell-surface activation markers after in vitro stimulation of human peripheral blood mononuclear cells with Streptococcus pneumoniae

The aim of this study was to describe the kinetics of the cytokine release and the expression of activation markers on lymphocytes after stimulation of peripheral blood mononuclear cells (PBMC) with whole killed Streptococcus pneumoniae. The cytokine release and the expression of CD25 and HLA-DR on T cells, and CD69 on T cells, B cells and NK cells, were measured at different times. Our results show that tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-10 and IL-12 reached maximal levels at 24 h, while IL-6, IL-8, TNF-beta and interferon (IFN)-gamma increased throughout the 1-week test period. The strains tested gave an increased expression of CD69 on all cell types, as well as an increase of CD25 and HLA-DR expression on T cells. The maximal CD69 expression was seen after 24 h on T cells and NK cells, while the B-cell expression of CD69 reached a plateau at the same time. All the cells still expressed CD69 on their surfaces after 1 week. In conclusion the results indicate that there was probably an early activation of monocytes leading to a polyclonal activation of lymphocytes.     

Expression of the CMRF-35 antigen, a new member of the immunoglobulin gene superfamily, is differentially regulated on leucocytes.

A new monoclonal antibody, CMRF-35, has been generated that recognized a 224 amino acid cell surface protein which is a novel member of the immunoglobulin gene superfamily. The antibody, raised against large granular lymphocytes (LGL), stains LGL, monocytes, macrophages and granulocytes but not platelets or erythrocytes. In addition, a subset of peripheral blood T lymphocytes (26.6 +/- 13.4% CD5+ cells) and B lymphocytes (13.7 +/- 6.8% CD20+ cells) stained with CMRF-35 but tonsil T and B cells were essentially negative. Expression of the CMRF-35 antigen (Ag) on different leucocyte populations was markedly influenced by stimulation of the cells with mitogens and cytokines. Activation of peripheral blood T cells with phytohaemagglutinin (PHA), or phorbol myristate acetate (PMA) and calcium ionophore (CaI) led to a decrease in the proportion of CMRF-35+ T lymphocytes. In contrast, PHA activation of tonsil T lymphocytes resulted in an increase in CMRF-35 Ag expression (47.1 +/- 1.5% CD5 cells at 6 days). An increase in CMRF-35 Ag was also seen on phorbol ester and CaI-activated tonsil B cells. No change in CMRF-35 expression on natural killer (NK) cells occurred following activation with interleukin-2 (IL-2) but the CMRF-35 Ag was down-regulated following Fc receptor stimulation. A moderate increase in CMRF-35 expression occurred during monocyte-macrophage differentiation and the expression of the Ag on monocytes was differentially regulated by interferon-gamma (IFN-gamma). This regulation of the CMRF-35 Ag on the leucocyte surface suggests that the molecule has an important function common to diverse leucocyte types.     

Distinct expression and inhibitory function of B and T lymphocyte attenuator on human T cells

B and T lymphocyte attenuator (BTLA) has been recently identified as a new inhibitory receptor of the CD28 superfamily, with similarities to cytotoxic T lymphocyte activation antigen (CTLA)-4 and programmed death (PD)-1. Engagement of BTLA on T lymphocytes can profoundly reduce the T cell receptor (TCR)-mediated activation. In this study, we generated four monoclonal antibodies (mAbs) against human BTLA. Using the produced mAb 8H9, the BTLA molecule was found to distinctly express on many subgroups of immunocytes and show a regulatory expression, which was in accordance with its unique ligand herpes virus entry mediator (HVEM) in the process of T cell activation. In addition, the expression of BTLA was increased in the CD4(+) and CD8(+) T cells of pleural fluid in lung cancer patients. Furthermore, we showed that the BTLA-induced negative signals could be triggered by mAb 7D7. Cross-linking of BTLA with mAb 7D7 suppressed T lymphocyte proliferation, downregulated the expression of T cell activation marker CD25, and inhibited the production of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, and IL-10.     

IL-7 modulates B cells survival and activation by inducing BAFF and CD70 expression in T cells

Interleukin-7 (IL-7) promotes the maintenance and activation of peripheral T cells, whereas it does not act directly on mature B cells due to the lack of IL-7Rα expression on these. We report here that, in spite of the insensitivity of B cells to IL-7, high concentration of IL-7 can lead to increased B cell survival and antibody production in the presence of T cells, without the use of any further B cell stimulatory signal. IL-7 promoted B cell activation through inducing CD70 expression on resting T cells, particularly on CD4+ memory cells. The interaction of CD70 molecules with the B cell costimulatory receptor CD27 led to B cell proliferation, the accumulation of CD38 + CD20- plasmablasts and antibody production. In addition, IL-7 treatment induced BAFF secretion from resting peripheral T cells thereby promoting B cell survival. IL-7 levels can increase in lymphopenic conditions, in autoimmune diseases or in patients receiving T cell regenerative IL-7 therapy. Based on our findings high IL-7 levels can lead to increased B cell activation by inducing the B cell regulatory proteins CD70 and BAFF in resting T cells. Such activity might be beneficial in short term immune-stimulatory IL-7 therapies; permanently increased IL-7 levels, on the other hand, can contribute to impaired B cell tolerance.     

Airway epithelial cells modify immune responses by inducing an anti-inflammatory microenvironment

The upper airways are prone to contact with pathogenic as well as non-pathogenic microbes, therefore immune recognition principles have to be tightly controlled. Here we show that human BEAS-2B bronchial epithelial cells inhibited secretion of the pro-inflammatory cytokines TNF-alpha and IL-12 by monocytes, macrophages and dendritic cells. This inhibitory effect could be transferred by supernatant of resting BEAS-2B cells and was also observed when primary murine tracheal epithelial cells were prepared. In contrast to inhibition of pro-inflammatory cytokine secretion epithelial cell-conditioned dendritic cells showed increased expression of IL-10 and arginase-1, thus displaying properties of alternative activation. Accordingly, Toll-like receptor-mediated up-regulation of CD40, CD86 and PD-L2 (CD273) on murine dendritic cells was reduced in the presence of bronchial epithelial cell supernatant. However, expression of negative regulatory PD-L1 (CD274) was increased and dendritic cell induced proliferation of T lymphocytes was diminished. Epithelial cells also showed a direct inhibitory effect on T lymphocyte proliferation and this was due to the constitutive secretion of TGF-beta by bronchial epithelial cells. Moreover, epithelial cell-conditioned T lymphocytes showed increased differentiation towards IL-10-producing Tr1 cells. The results indicate that bronchial epithelial cells induce a non-inflammatory microenvironment that regulates local immune homeostasis.     

Induction of proliferation and monocytic differentiation of human CD34+ cells by CD137 ligand signaling

CD137 is a member of the tumor necrosis factor receptor family and is involved in the regulation of activation, proliferation, differentiation, and cell death of leukocytes. Bidirectional signaling exists for the CD137 receptor/ligand system, as CD137 ligand, which is expressed as a transmembrane protein, can also transduce signals into the cells on which it is expressed. In this study, we have identified expression of CD137 in human bone marrow and expression of CD137 ligand on a subset of CD34+ cells. Cross-linking of CD137 ligand on CD34+ cells by CD137 ligand agonists induces activation, prolongation of survival, proliferation, and colony formation. CD137 ligand agonists induce differentiation of early hematopoietic progenitor cells to colony-forming units-granulocyte/macrophage and subsequently to monocytes and macrophages but not to dendritic cells. These data uncover a novel function of CD137 and CD137 ligand by showing their participation in the growth and differentiation of hematopoietic progenitor cells.     

Regeneration and tolerance factor is expressed during T-lymphocyte activation and plays a role in apoptosis

Regeneration and tolerance factor (RTF) is a protein cloned from the thymus and expressed on B lymphocytes in normal pregnancy, B lymphocytic leukemia lines, and T and B lymphocytes in individuals with HIV infection. Findings, using the Jurkat T-cell model, revealed that RTF is upregulated after activation and anti-RTF antibody-induced apoptosis. In this article anti-RTF antibody-induced apoptosis of both unstimulated and activated T lymphocytes. RTF expression was examined in human PBMC or purified T lymphocytes after their in vitro activation. Kinetic studies indicated maximal RTF cell surface expression on activated T lymphocytes occurred between expression of the early activation antigen CD69 and the IL-2alpha receptor (CD25) by multiparameter flow cytometry. RTF receptor expression correlated with Fas (CD95) and CD25 receptor expression (r2 = 0.6 and 0.5, respectively). RTF surface expression was dependent on the stimuli used to activate T lymphocytes. T lymphocytes obtained maximal RTF expression when activated through the TCR signal complex using anti-CD3epsilon antibody alone when compared with T lymphocytes activated with costimulation provided by anti-CD28 antibody alone or with anti-CD28 and anti-CD3epsilon antibody. RTF is expressed under conditions of both activation and anergy. The RTFs increased concentration on the surface of anergic T cells may protect these cells from apoptosis because increased RTF concentrations inhibited anti-RTF induced apoptosis. These data further characterize the expression of RTF on activated T lymphocytes and the role of anti-RTF antibody in T-lymphocyte apoptosis.     

The distribution of IL-13 receptor α1 expression on B cells,T cells and monocytes and its regulation by IL-13 and IL-4

To study the expression of IL-13 receptor α1 (IL-13Rα1), specific monoclonal antibodies (mAb) were generated. Surface expression of the IL-13Rα1 on B cells, monocytes and T cells was assessed by flow cytometry using these specific mAb. Among tonsillar B cells, the expression was the highest on the IgD⁺ CD38⁻ B cell subpopulation which is believed to represent naive B cells. Expression was also detectable on a large fraction of the IgD⁻CD38⁻ B cells but not on CD38⁺ B cells. Activation under conditions which promote B cell Ig class switching up-regulated the expression of the receptor. However, the same stimuli had an opposite effect for IL-13Rα1 expression levels on monocytes. While IL-13Rα1 mRNA was clearly detectable in T cell preparations, no surface expression was detected. However, permeabilization of the T cells showed a clear intracellular expression of the receptor. A soluble form of the receptor was immunoprecipitated from the supernatant of activated peripheral T cells, suggesting that T cell IL-13Rα1 might have functions unrelated to the capacity to form a type II IL-4 / IL-13R with IL-4Rα.     

Involvement of CD44 exon v10 in B-cell activation

Abstract: The family of CD44 glycoproteins has been suggested to be involved in lymphocyte homing, maturation and activation. Using in vitro blocking studies with a monoclonal antibody, we here addressed the question of functional activity of CD44 variant exon v10 (CD44v10) in B-cell activation. We became interested in this question by the observation that CD44v10 was transiently expressed on activated T cells, B cells and mono-cytes as well as on a subpopulation of bone marrow cells. A potential ligand, as revealed by staining with a CD44v10 receptor globulin, was only detected on monocytes. Anti-CD44v10 had no major impact on T-cell activation and no influence on primed B cells, but interfered with the mounting of a primary B-cell response to T-independent and T-dependent antigens. Addition of anri-CD44v10 at different stages during the activation process revealed that CD44v10 was not engaged in B-cell-T-cell interactions. The antibody exerted some effect on monocyte activation as defined by a slight decrease in IL-1 production, but most efficiently inhibited antigen-specific as well as mitogen-induced B-cell activation when present during the co-culture of virgin B cells with monocytes. These findings, together with the observation that a CD44v10 ligand was only detected on monocytes but not on lymphocytes, point towards a requirement for CD44v10 in a B-cell-monocyte interaction. Furthermore, since activation of B cells by engagement both of the B-cell receptor and of mitogen receptors was inhibited by anti-CD44v10, the data suggest that a costimulatory function of CD44v10 proceeds independent of the B-cell receptor.     

Requirements for activation of human peripheral blood T cells by mouse monoclonal antibodies to CD3

The present study was undertaken in an attempt to reconcile the conflicting results concerning the signals required for the activation of human resting T cells by antibodies to the T-cell receptor/CD3 complex (Ti/CD3). For this purpose we have used highly purified peripheral blood T cells, depleted of monocytes and of preactivated Ia + T cells, to the extent that they were unable to proliferate to interleukin 2 (IL-2) alone or to optimal doses of phytohemagglutinin (PHA). To further minimize the contribution of contaminating monocytes, we used the anti-CD3 mAb, Leu-4, and cells from Leu-4 nonresponder subjects, whose monocytes we show completely fail to bind the Leu-4 mAb. The parameters of T-cell activation which we measured were rises in intracellular free calcium ion [Ca2+]i, IL-2 receptor expression IL-2 production, and cell proliferation. Our results indicate that induction of proliferation of resting T cells requires at least two signals. Signal one is best delivered by multivalent anti-CD3 mAb, such as Leu-4 mAb covalently linked to Sepharose 4B (Seph-Leu-4), or with Leu-4 mAb and anti-mouse IgG. These reagents crosslink the CD3 receptor complex on the T cell, and result in a rise in intracellular [Ca2+]i, in expression of receptors for IL-2, and in proliferation upon addition of IL-2. In contrast, purified T cells exposed to soluble Leu-4 mAb do not exhibit a rise in intracellular [Ca2+]i, do not express receptors for IL-2, and do not proliferate upon addition of IL-2, indicating that the valency of anti-CD3 mAb is critical for the delivery of the first activation signal to the T cell. The essential step of crosslinking of CD3 antigens on T cells by anti-CD3 mAb is normally mediated by monocytes which have bound anti-CD3 mAbs via their Fc receptors. Monocytes from Leu-4 nonresponder subjects, which we show fail to bind Leu-4 mAb, fail to crosslink CD3 antigens on T cells, resulting in failure of T-cell activation. The second signal needed for the proliferation of T cells whose Ti/CD3 complexes are crosslinked is IL-2. IL-2 production by such T cells required a monocyte delivered signal, which must be delivered to these T cells simultaneously with the crosslinking of their Ti/CD3 antigens. This IL-2-inductive signal can be delivered by both Leu-4 nonresponder and Leu-4 responder monocytes, indicating that delivery of this IL-2 inductive signal is independent of anti-CD3 mAb binding by monocytes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Expression of functional insulin-like growth factor-1 receptor on lymphoid cell subsets of rats.

It has become evident that insulin-like growth factor-1 (IGF-1) acts as a growth factor for immune cells, yet the precise regulatory role of IGF-1 in the immune system is unknown. The aim of this study was to examine the distribution of IGF-1 receptors on rat lymphoid cells. A flow cytometric method was used, with a biotinylated and functionally active IGF-1 analogue, namely des(1-3)IGF-1, which binds well to IGF-1 receptor but poorly to IGF binding proteins, followed by phycoerythrin-conjugated streptavidin (PE-SA) staining. Our results showed that IGF-1 receptors were readily detectable on a wide variety of the immune cells, including T cells, B cells and monocytes, but the binding capacity for IGF-1 was monocytes > B cells > T cells, as determined by titration experiments. Furthermore, the level of expression on resting CD4+ T lymphocytes was greater than on CD8+ cells, and the concentration of biotin-des(1-3)IGF-1 required to demonstrate the binding to IGF-1 receptor on CD8+ cells (68 nmol/l) was 200-fold higher than for CD4+ cells (0.34 nmol/l), indicating that most of the IGF-1 receptor on CD8+ cells represented lower affinity sites. The level of IGF-1 receptor expression was increased several-fold after concanavalin A stimulation on both CD4+ and CD8+ T-cell subsets. Kinetic analysis of the expression of IGF-1 receptor and its association with interleukin-2 receptors (IL-2R) following activation showed a similar pattern, with no significant differences in the ratio of IGF-1 receptor: IL-2R per cell during the 3 days of cell culture. Our studies suggest that biological activities of IGF-1 include direct stimulation of immune cells, and that expression of IGF-1 receptor may have a role in regulation of T-cell function.